Figure 50a, and more flexible. It would not require accurate alignment to 
the work site as would the more complicated machine, because its control 
system could be indexed to compensate for angular displacement of the 
chassis from the desired geographical direction. |t could work all around 
"itself, giving a much greater working area without relocation, simplifying 
the control problem further. 
An additional simplification in machine development would be 
accomplished by adapting a commercially available hydraulic crane as shown 
in Figure 51. However, the contro! problems would be further complicated 
in that this machine would use full polar coordinates—it would see the world 
as a sphere. Within limits it would be able to excavate even under itself. 
The preceding discussion of the earth milling (or controlled dredging) 
concepts by no means proposes to eliminate the possibility of adapting con- 
ventional earthmoving techniques and machines to the ocean floor. At least 
one remotely controlled bulldozer is known to be available from Japan (Anon- 
ymous, 1968). It would be comparatively simple to power a small bulldozer with 
individual hydraulic motors (Nuttall, 1970a) on the tracks. The combined 
problems of turbidity during the work period, inaccessability for control, 
and the inability to drill shallow holes for piling, etc. inherent in conventional 
earthmoving makes this approach relatively unattractive in comparison to 
milling. Bulldozing is a cut-and-try process relying heavily on the operator's 
abilities and the making of successive cuts to achieve grade. The potential for 
simple and accurate profiling is obviously not there. 
It is a major thesis of this study that accurate profiling of work site 
to accept the prefabricated structures is needed for installation of prefabri- 
cated installations. In the realm of manufacturing, this type of control is 
routinely and precisely obtained with such machines as mills and surface 
grinders. In particular, the numerically controlled vertical spindle mill is 
a highly controllable, mechanically simple machine capable of intricate pro- 
filing, limited only by the sophistication of controls. The previous discussion 
provides an outline of the proposed approach for achieving the same capabil- 
ities in machining the surface of the ocean bottom. Numerical or computer 
control according to a preplanned profile makes accurate profiling possible 
in a remote location without visibility during excavation. 
On the basis of early stages of the study reported here, a contract for 
a systems analysis and preliminary design of a remotely controlled seafloor 
excavation machine was let in mid-1969 to the Northrop Corporation. The 
report of the work accomplished under this contract will be issued In early 
1971. 
60 
